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Inventories - Narrative (Detail) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Inventory [Line Items] |  |
Inventory, materials and supplies | $ 25,319 | $ 24,008
Railroad, Utilities and Energy [Member] | Other Assets [Member] |  |
Inventory [Line Items] |  |
Inventory, materials and supplies | $ 3,200 | $ 3,000

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